Individuals with autism spectrum disorders (ASD) who cannot speak at all or not intelligibly are frequently taught to use aided augmentative and alternative communication (AAC). The majority of the research on the use of AAC with individuals with ASD has been single-case research studies. This investigation involved a meta-analysis of the single-case research on the use of aided AAC with individuals with autism spectrum disorders (ASD), investigating the differential impacts of AAC by participant characteristics. An effect size measure, the Improvement Rate Difference (IRD) was used to analyse 24 single-case studies. Two research questions were investigated concerning (a) the impact of AAC interventions on individuals diagnosed with subcategories of ASD and comorbid conditions, and (b) the effects of AAC interventions on individuals in different age groups. Results indicated that participants with ASD and no additional diagnoses had better outcomes than others and that participants with ASD and developmental disabilities outperformed participants with ASD and multiple disabilities. Further, preschool-aged participants had better outcomes than elementary-aged and secondary- aged participants. Participants in all diagnostic categories and age ranges had moderate or better effects.